This invention is related to drive axles for heavy vehicles, such as wheel loaders, of the type having drive hub assemblies rotatably mounted to the respective ends of the axle housing and having planetary gear drives therein and, more particularly, to an apparatus for transferring fluids from the nonrotating axle housing to the rotating drive hub assembly.
It is previously known to use a nonrotatable spacer ring to fix the axial position of the inner bearing mounting the planetary gear drive hub assembly on an axle housing. Such is shown, for example, in Chamberlain U.S. Pat. No. 4,140,198. However, the prior art drive axle assemblies, as also shown in Keese U.S. Pat. No. 4,037,694, and Sidles, Jr. et al. U.S. Pat. No. 4,142,615, utilized a pool of oil for cooling and lubricating and hydraulic passages in the fixed spindle for actuating the brake pack. In the referenced copending applications, a brake pack is provided in the drive hub assembly wherein all portions of the brake pack and the actuating means therefor rotate relative to the spindle. Consequently, it requires that for actuating the brake, the actuating fluid be transferred from the nonrotating spindle to the rotating hub assembly.
Accordingly, a primary object of the invention described and claimed herein is to provide a drive axle assembly of the type described with a means associated with the axle spindle for establishing a fluid tight transfer of operating fluid to the drive hub assembly.
A more specific object is to provide a drive axle assembly with a structure for communicating brake actuating fluid pressure from the stationary axle structure to the rotatable wheel hub assembly.
A further object of the invention is to provide in a drive axle assembly a structure for communicating lubricating and cooling fluid under pressure from the stationary axle structure to the drive and brake components in the rotating wheel hub.
Still a further object of the invention is to provide the drive axle assembly with a housing for stationary portion of the primary oil face seal located between the environment and the interior of the axle structure.
Yet another object of the invention is to circulate the pressurized fluid for the drive and brake components past the aforesaid seal to also effect cooling thereof.
A more specific object is to provide in a drive axle assembly a single structure meeting, in cooperation with the surrounding structure, all of the above objects while also functioning as the prior art bearing spacer ring which eliminates a stress concentrating sharp corner on the spindle.
The above objects and others which will become apparent hereinafter are specifically met in a drive axle assembly including a housing structure having a fixed spindle, a nonrotatable spacer ring disposed about the spindle and a drive hub rotatably mounted on the spindle by bearings, one of which abuts the spacer ring. The spacer ring has a brake apply fluid inlet to an interior passage which opens to a first sealed annular cavity between the spacer ring and the hub. The exterior of the spacer ring defines in conjunction with the drive hub a second low pressure cavity therebetween enclosed by a radial face seal having a rotating portion disposed in the hub and a non-rotating portion disposed in the spacer ring. Lubricating and cooling fluid is pumped through the second cavity to cool the face seal and continues through passages in the drive hub to provide a nearly continuous flow to the drive and brake components in the hub assembly. The specific location of the brake apply cavity interiorly adjacent the lower pressure lubricating cavity also minimizes the effect of small leakages past the seals of high pressure in the brake apply cavity.